Sail servo confusion for a 1 meter

[Ray C]

I just recieved a Voyager, my first r/c sailboat, and am looking for a sail servo. The most reccomended is the Futaba S3801, which will not fit the servo mount on this boat without cutting and modification, so I wanted to look around to see if anything else could be used that would fit. I found a site that reccomended a Hitec HS-645mg, 133 oz/in, for use with a Victoria, probably powerfull enough for recreational sailing with the Voyager. Hitec also has the HS-5645 at 168 oz/in that is the same size. Another plus is that the price is about half of a S3801. However, in the specs neather one is reccomended for sailboat applications, even though they are waterproof. What problems could I run into using one of the Hitecs for a sail servo?

Also, could 7.2 volts be used to the servos without harm?

Thanks
Ray C

[SecretSquirrel]

I use the 645 MG in my Victoria and it works fine. Just about any servo can be used to make an arm type sail winch. Most manu's only recommend their VERY slow and VERY heavy Drum winches for sailboat applications.

I do not have any personal experience using the 5645, but the only real difference is the 5 designates a Digital servo (ie Digital 645). In general, digital servos center better and have better initial torque but are more expensive and draw more current (less battery life).

I would check the Hitec RCD FAQ's to find out if either will work with 7.2 volts. Most prefer no more than 6V but you could ask.

Also, Hitec customer service is outstanding.
Regards,
Jim

[pompebled]

Hi Ray,

Attached is a picture of my sailservo in the Voyager.

I've cut out the servotray (don't cut out the front section, the keelslot will leak, don't ask...) and made a new mounting plate for the 1/4 scale servo which I glued in place.

Works like a charm.

As you can see in the picture, I also adapted the rear tray to accept a standard servo for the rudder.

Regards, Jan.

(Watch your pm box)

[SecretSquirrel]

I only race my Victoria (top 15 at NA's) and the 645 MG is plenty. Because I am trying to minimize weight I switched to a HS81MG micro servo for the rudder. It has plenty of torque for me.

Regards,
SS

[Ray C]

Thanks Jan,Jim, I am understanding things better now. Another thing I would like to know is how many total degrees of rotation do you get with your servos?

Thanks
Ray

[pompebled]

Another thing I would like to know is how many total degrees of rotation do you get with your servos?

Thanks
Ray

My GWS IQ-900BB rotates 90 degrees (including trim).

I use a "computer" transmitter (Graupner's MC-10) which allows me to extend the rotation angles of the servo's, a useful feature.

Combined with the sheet configuration for the Voyager, this is sufficient sheet travel.

Also, could 7.2 volts be used to the servos without harm?
No, the servo electronics are generally designed for use with 4.8-6V, a freshly charged 7.2V battery (six cells) can reach 8V+, upon connecting, you'd probably fry your electronics instantly.

For use in the Voyager 7,2V is pointless, yesterday I've sailed for five hours straight, on a five cell receiverpack with 2300mAh capacity.
The recharge was 1500mAh.
The 1/4 scale sailservo I use is a potent one, so I have an average of 300mAh per hour, in conditions just above freezing.

Regards, Jan.

[Ray C]

What size and angular rotation would be good for the rudder servo. The ones that came with my Spektrum DX6 transmitter are quite small, rated at 17 in/oz. Could they be used, or do I need one up in the 30s or more?

Thanks
Ray

[SecretSquirrel]

I dont know how big the rudder on your boat is, but I would recommend 35-60 oz/in at 6.0V. In my Vic I used to have a standard sized Futaba 3003 - 57 oz/in. I simplified the linkage and switched to the HS81MG (micro) - 42 oz/in @ 6.0V. Much lighter and faster with a little less torque. I have had a couple of issues turning down at the top mark, but I think that was unrelated as I lost my rudder shortly after (fell out the bottom).

I would post my sortable servo comparison sheet but RCGroups does not support Excel files. If anyone would like a copy please PM me.

I have made a column called Torque/Speed @ 6.0V. It takes the Torque at 6.0V and divides by Speed at 6.0V. So, a very strong slow servo rates lower than a slightly weaker, but much faster servo would. I though it showed a nice balance.

Using that math the HS645MG rates very highly for use as a sail servo. For a rudder servo the decision starts with size (standard, mini, or micro). All have very suitable options.

The cheapest way to go for the rudder is use what came with the radio.

Regards
SS

[Ray C]

Your servo comparison sheet sounds very usefull, but I don't have Excel eather. There are so many choices and variations available it is very confusing. Thanks for all your help.

Ray

[pompebled]

What size and angular rotation would be good for the rudder servo. The ones that came with my Spektrum DX6 transmitter are quite small, rated at 17 in/oz. Could they be used, or do I need one up in the 30s or more?

Thanks
Ray

Hi Ray,

For your Voyager, a standard servo is sufficient.

As you can see in the pic I added before, I use the middle hole in the servo arm, the rudder arm uses the outside one.
My rudder throw is 30 degrees to each side and the boat steers quite well, more rudder throw would start to act as a break...

Regards, Jan.

[SecretSquirrel]

Jan,

Nice work on the double sided arm. I wish I could cut carbon that straight :)

Regards,
SS

[pompebled]

Jan,
Nice work on the double sided arm. I wish I could cut carbon that straight :)
Regards,
SS

That's a matter of a steady hand, a jig-saw, a few sawblades for metal and a piece of 1mm carbon sheet.
I used the vacuum cleaner to suck up the carbon dust, during the sawing and subsequently wet-sanded the burrs away.

Always wear protection when working with these kind of materials!

Regards, Jan.

[SecretSquirrel]

Sorry to hijack the thread, but where do you get 1mm Carbon? I can usually only find 3 & 5mm at the LHS.

Regards
SS

[wjbite]

I have two Victorias.
The sail sheet servos on them are
Hitec 645 and
Futaba 3801
The futaba has LOTS more swing than the Hitec.
The Futaba is about 140 deg: the HiTec about 100 deg. It is so much more throw I am experimenting with eliminating the sheet turning point on the arm and replacing it with a solid attachment while moving the sail end of the sheets closer to the masts. My hope is that this will eliminate some of the friction and some of the tangling issues.

[pompebled]

Sorry to hijack the thread, but where do you get 1mm Carbon? I can usually only find 3 & 5mm at the LHS.
Regards
SS

This particular piece was a leftover from a hull I got at eBay Germany, so I guess the previous owner got it locally.

For a sailarm this size, the 1mm is strong enough, I kept it rather wide to eliminate the flex, works like a charm.

Regards, Jan.

[SecretSquirrel]

I used to have the Futaba 3801 in my Vic, but I needed to lose some weight so I switched to the 645MG. Also I have a double sided arm so I dont need more than 100° of travel.

Regards,
SS

[zedfor]

don't make a choise untill you take a look at the RMG winch from Australia.

[pompebled]

don't make a choise untill you take a look at the RMG winch from Australia.

I don't doubt the quality of the RMG winches, but I do doubt that someone who buy's a Voyager, is willing to spend roughly the same amount on a winch...

Regards, Jan.

[SecretSquirrel]

The RMG is great but is a drum winch better suited to bigger boats (IMO). A double sided arm will give you much FASTER sheet in/sheet out, but no where near the torque possible with the RMG. And like pompebled said, the RMG costs $165.

Regards,
SS

[Vernon Hunt]

:rolleyes: Try Servo City, they have what you need.